"This 24/7 lockdown life is slowly driving me insane and killing (me)," Spector, 69, wrote in a letter to a fan that was posted online on Friday.

Spector, who revolutionized pop music in the 1960s with his "Wall of Sound" production technique, was convicted in April of the 2003 murder of actress Lana Clarkson and later sentenced to a minimum of 19 years in prison.

In the letter written in July to a fan that was obtained by pop culture website Gawker.com, Spector complained that he was unable to "say goodbye" to anyone, or organize his business affairs before going to prison.

"How cruel but apparently not unusual," Spector wrote. "And they call this a 'civilized' society. Bugs live more civilized beneath their rocks!".

Spector wrote the four-page, handwritten letter to a woman in Texas, sending it from prison in California.

At the height of his fame, Spector worked with The Ronettes, The Beatles, Cher, the Ramones and Leonard Cohen, but in the 1980s he withdrew from music. He quietly married singer and actress Rachelle Short in 2006.